1. Field of Invention
The invention relates to a drive unit for a vehicle, and is applicable to a hybrid vehicle, etc., and more particularly relates to a drive unit for a vehicle which is of a type (a so-called 2-motor split type) having first and second motors (conceptually including a generator) and has a structure able to effectively restrain reaction force during engine starting on the basis of the driving of the first motor.
2. Description of Related Art
The so-called 2-motor split type structure is conventionally mounted to a vehicle, for example, the automobile identified as a PRIUS®, and is practically used as a hybrid drive unit. In this type, an output from an internal combustion engine (hereinafter also simply called the engine) is distributed to the first motor (generally called the generator) and the running output side by a planetary gear. The output torque of the planetary gear is steplessly controlled by mainly controlling the operation of the first motor as the generator. Further, as necessary, the torque of the second motor (generally called a drive motor) is synthesized with the planetary gear output torque and is outputted to an output shaft.
The hybrid drive unit of the 2-motor split type in practical use is mounted in the vehicle as a drive unit for front engine and front drive (called FF in this specification). However, it is also considered that the hybrid drive unit of front engine and rear drive (called FR in this specification) type can be mounted in the vehicle.
In the above hybrid drive unit, for example, while a crankshaft is associatively rotated on the basis of the driving force of the first motor, the engine can be started in a state in which the operation of a predetermined rotating element of the planetary gear is restrained through a drive wheel engaged by a foot brake, the output shaft connected to this drive wheel, etc., i.e., in a state in which reaction force in the planetary gear using the driving of the first motor is restrained. However, in this case, when the reaction force based on the driving of the first motor is transmitted to the drive wheel side through the output shaft, etc., torque is instantaneously generated in the retreating direction of the vehicle body and gives an uncomfortable feeling to persons in the vehicle.
Therefore, for example, it is considered to control the operation of the second motor such that the second motor is approximately operated in synchronization with the driving of the first motor to restrain the reaction force in the planetary gear using the driving of the first motor by the output torque of the above second motor so as not to give the above uncomfortable feeling to the persons in this vehicle.